Photo of Dawn, Courtesy of LeeAnn
The name Cushing's Disease stems from Dr. Harvey Cushing, a human physician and the first person to describe the symptoms in 1932. Cushing's Disease refers to a collection of symptoms seen when there is an excess of cortisol. In the horse, what is commonly called Cushing's Disease is caused by hyperplasia (enlargement) or adenoma (benign tumor) in a portion of the pituitary called the pars intermedia (intermediate lobe). Therefore, the more accurate term is Pituitary Pars Intermedia Dysfunction (PPID).
Horses with advanced PPID and classical coat changes are often recognized by symptoms alone. However, over the years it has become very clear that long before coat changes develop, the first symptom of an early PPID case is often unexplained fall laminitis. Observant horse owners & veterinarians have been able to recognize much earlier signs of PPID before the advanced coat changes often allowing early and effective treatment of the disease.
Subtle signs include weight loss/muscle loss particularly across the topline which may also be accompanied by a pot belly appearance or subtle coat changes such as extra long, coarse and/or thick hair during the winter often attributed to an unusual winter or later than normal spring shedding with perhaps only guard hairs remaining on the neck or belly often attributed to old age. However, a combination of these symptoms may indeed be a collection of early PPID signs especially if it involves seasonal laminitis!
Symptoms Of Pituitary Pars Intermedia Dysfunction (PPID) / Cushing's Disease
- Muscle loss, often most noticeable across the topline
- Weight loss and pot belly appearance are common and may be seen with patchy fat deposits developing in the neck and around the tail head
- Excessive drinking and urination
- Laminitis often occurring in the Fall
- Either excessive sweating (hyperhidrosis) or failure to sweat (anhidrosis)
- Skin darkening, often with thickening and scaling
- Increased susceptibility to infections
- Poor resistance to internal parasites
- Development of allergies and hypersensitivities (e.g. vaccinations, flies)
- Slow spring shedding with long, coarse & sometimes curly coat with failure to shed completely occurring in advanced cases